presented at the comsol conference 2009 milan comsol ... · heat transfer throughheat transfer...
TRANSCRIPT
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COMSOL Multiphysics as a Tool to Increase Safety i th H dli f A t l C li d I l d i Fiin the Handling of Acetylene Cylinders Involved in Fires
Fabio FerreroFabio Ferrero
BAM Federal Institute for Materials Research and TestingDivision II.1 “Gases, Gas Plants” Working Group “Safety Related Properties of Gases”Working Group Safety Related Properties of GasesUnter den Eichen 87, D-12205 Berlin, Germany
COMSOL CONFERENCEMilan, October 14-16 2009
Presented at the COMSOL Conference 2009 Milan
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• Acetylene (C2H2) is commonly used for cutting and welding purposes
Background
Acetylene (C2H2) is commonly used for cutting and welding purposes • Normally stored in compressed gas cylinders• Acetylene cylinders involved in fire can burst
Explosion of a fully charged 40 dm3 acetylene cylinder (bonfire test)
P i id t• Previous accidents:- Schutterwald, Germany, accident in a private workshop (1994)- Brisbane, Australia, accident in an acetylene factory (1999)- Dallas, USA, accident in a gas factory (2007)
ConsequencesEconomical and human losses (fireball, ejection of fragments)
COMSOL CONFERENCEMilan, October 14-16 2009
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I t t t k
Objectives
Important to know:• heating up process
- time to explosion
• critical temperature / pressure in the cylinder- acetylene can decompose with high heat release (226 kJ/mol)
• cooling with water- the cylinder can be safely handled after the firey y
experiments and/or simulations
A mathematical model to predict the heat transfer in the acetylene cylinder has been developed and solved in COMSOL Multyphysics
COMSOL CONFERENCEMilan, October 14-16 2009
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Acetylene Cylinder
Acetylene cylinder:
- steel wallsteel wall
- the inside is not a free space, but a complex system
copyright: www.bam.de
COMSOL CONFERENCEMilan, October 14-16 2009
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Acetylene Cylinder
Composition cylinder inside:- porous material
( / )- acetone (liquid/vapour)- acetylene (free/dissolved)
copyright: www.bam.de
COMSOL CONFERENCEMilan, October 14-16 2009
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Acetylene Cylinder
Composition cylinder inside:- porous material
( / )- acetone (liquid/vapour)- acetylene (free/dissolved)
Free space- free acetylene
acetone vapour- acetone vapour
copyright: www.bam.de
COMSOL CONFERENCEMilan, October 14-16 2009
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Simulation: geometry & mesh
Geometry (50 dm3):
Implementation in COMSOL
2D Axial symmetric (computing time reduction)
Mesh- elements: 10740
nodes: 6045- nodes: 6045- degrees of freedom: 40633
COMSOL CONFERENCEMilan, October 14-16 2009
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Simulation: domains and equations
(V= 50 L)
Heat transfer through conduction
Tλ=tTcρ iipi grad div,
(1)
COMSOL CONFERENCEMilan, October 14-16 2009
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Simulation: domains and equations
Heat transfer through conduction
Tλ=tTcρ iipi grad div,
(1)
i=1 steel wall (COMSOL library)
(i=1)
COMSOL CONFERENCEMilan, October 14-16 2009
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Simulation: domains and equations
Heat transfer through conduction
Tλ=tTcρ iipi grad div,
(1)
i=1 steel wall (COMSOL library) i=2 porous material / acetone (g,l) / acetylene (d,f)
( l i l f ti )(i=2) (polynomial functions)
COMSOL CONFERENCEMilan, October 14-16 2009
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Simulation: domains and equations
Heat transfer through conduction
Tλ=tTcρ iipi grad div,
(1)
i=1 steel wall (COMSOL library) i=2 porous material / acetone (g,l) / acetylene (d,f)
( l i l f ti )(polynomial functions)i=3 acetylene (g) (polynomial functions)
(i=3)
COMSOL CONFERENCEMilan, October 14-16 2009
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Simulation: domains and equations
No decomposition / No pressure
Heat transfer through conduction
Tλ=tTcρ iipi grad div,
(1)
i=1 steel wall (COMSOL library) i=2 porous material / acetone (g,l) / acetylene (d,f)
( l i l f ti )(polynomial functions)i=3 acetylene (g) (polynomial functions)
(i=3)
COMSOL CONFERENCEMilan, October 14-16 2009
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Simulation: domains and equations
Heat transfer through conduction/convectionHeat transfer through conduction/convection
(2)TucρTλ=tTcρ jPjjjPj grad grad div ,,
Momentum equation (Navier Stokes)
up=uuu
2 (3)up=uu
t jjj
(3)
Continuity equation
0=ut j
j
(4)
j=1 air (heating up) j=2 water (cooling)
(j)
COMSOL CONFERENCEMilan, October 14-16 2009
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Simulation: boundary settings (heating)
or14)( uzzuzuu (5)
Flame velocity field
maxmax or14)( uzzuzuu
maxmax or14)( vrrvrvv
(5)
(6)
Both currents are at Tflame = 1000°C
COMSOL CONFERENCEMilan, October 14-16 2009
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Simulation: results (heating)
Initial temperature: 15°C T [°C]
vmax = 5 m/s
umax = 2 m/s
Initial temperature: 15 C
1800
T [ C]
t = 1800 s
COMSOL CONFERENCEMilan, October 14-16 2009
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Simulation: results (heating)
Initial temperature: 15°C T [°C]
vmax = 5 m/s
umax = 2 m/s
Initial temperature: 15 C
1800
T [ C]
t = 1800 s
COMSOL CONFERENCEMilan, October 14-16 2009
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Simulation: results (heating)
Initial temperature: 15°C T [°C]
vmax = 5 m/s
umax = 2 m/s
Initial temperature: 15 C
1800
T [ C]
Gas Cavity
t = 1800 s
T [°
C]
Porous Material 1
Porous Material 2
Critical temperatures can be achieved
t [s]
can be achieved
p0 = 10 bara, T=370°C(V= 3 dm3)
PM1PM2 GC
COMSOL CONFERENCEMilan, October 14-16 2009
(V 3 dm )
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Simulation: results (heating)
Initial temperature: 15°C T [°C]
vmax = 5 m/s
umax = 2 m/s
Initial temperature: 15 C
1800
T [ C]
Gas Cavity
t = 1800 s
T [°
C]
Porous Material 1
Time to explosion
Porous Material 2
p
t [s]
Critical temperatures can be achieved
PM1PM2 GC
can be achieved
p0 = 10 bara, T=370°C(V= 3 dm3)
COMSOL CONFERENCEMilan, October 14-16 2009
(V 3 dm )
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Simulation: results (heating)
Temperature in the gas cavity as a function of: upward gas velocity (range 0 4 m/s)Temperature in the gas cavity as a function of: - upward gas velocity (range 0-4 m/s)- side wind speed (range 0-2 m/s)
600
800
atur
e [°
C]
0.000112.5225.0337.5450.0562.5
600
800
ure
[°C
]
0.000112.5225.0337.5450.0562.5
t = 640 s
0 5
0
200
400
2
4
Tem
pera
/s]
675.0787.5900.0
0
200
400
2
4
m/s]
Tem
pera
tu 675.0787.5900.0
t = 1800 s
0.51.0
1.52.0
0 v max [m
/s
umax [m/s]
0.51.0
1.52.0
0
v max [m
umax [m/s]
[initial temperature: 15°C]
find optimum values
Strong effects on the simulations
COMSOL CONFERENCEMilan, October 14-16 2009
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Simulation: boundary settings (cooling)
Water velocity field
maxmax or14)( vrrvrvv (7)
The current is at Twater = 20-80°C
COMSOL CONFERENCEMilan, October 14-16 2009
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Simulation: results (cooling)
Initial temperature
Water temperature
Time to 350°C
Time to 300°C
[°C] [°C] [h] [h][ C] [ C] [h] [h]400 20 10.1 13.8400 30 10.3 14.1400 80 10 5 15 5400 80 10.5 15.5
Take with caution:- 400°C may be too conservative- 400 C may be too conservative- include acetylene reaction (decomposition)
vmax = 1 m/s
COMSOL CONFERENCEMilan, October 14-16 2009
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Conclusions / Future Work
ConclusionsCOMSOL Multiphysics can help in increase the safe handling of acetylene cylinders involved in fire by predicting the:cylinders involved in fire by predicting the:
- time to explosion due to fire exposure- duration of the cooling with water after the fire
Future workcomparison with experiments (some have been already performed)- comparison with experiments (some have been already performed)
- determination of critical temperatures/pressures for the decomposition- inclusion of the pressure in the model
inclusion of the decomposition reaction- inclusion of the decomposition reaction
COMSOL CONFERENCEMilan, October 14-16 2009
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COMSOL Multiphysics as a Tool to Increase Safety i th H dli f A t l C li d I l d i Fiin the Handling of Acetylene Cylinders Involved in Fires
Fabio FerreroFabio Ferrero
BAM Federal Institute for Materials Research and TestingDivision II.1 “Gases, Gas Plants” Working Group “Safety Related Properties of Gases”Working Group Safety Related Properties of GasesUnter den Eichen 87, D-12205 Berlin, Germany
COMSOL CONFERENCEMilan, October 14-16 2009